1. Technical Field
The present invention relates to low-cracking-occurrence GaN single-crystal masses and to methods of their manufacture, as well as to low-cracking-occurrence semiconductor devices incorporating the GaN single-crystal masses and to methods of manufacturing the devices.
2. Description of the Related Art
As a material for short-wavelength optoelectronic devices, power electronic devices, and other semiconductor devices, attention is being focused on bulk single-crystal gallium nitride (GaN), which has a 3.4 eV energy bandgap and a high thermal conductivity.
A problem with such GaN single-crystal masses is that because they are of low toughness despite being highly hard, when the GaN single-crystal is being grown, and/or when the grown GaN single-crystal is being processed into substrate form, and/or when an at least single-lamina semiconductor layer is being formed onto a single-crystal GaN mass in substrate form to fabricate semiconductor devices, cracks will occur in the GaN single-crystal mass and/or in the semiconductor devices, leading to a drop in yield of the platelike GaN single-crystal masses (GaN single-crystal substrates) and/or semiconductor devices.
The elastic constants, meanwhile, of such GaN single-crystal masses have been measured or calculated by a variety of techniques, on crystal obtained by several different growth methods. Examples that may be cited include: R. B. Schwarz et al., “Elastic Moduli of Gallium Nitride,” Applied Physics Letters, Volume 70, Issue 9, 1997, pp. 1122-1124 (Non-Patent Reference 1); T. Deguchi et al., “Structural and Vibrational Properties of GaN,” Journal of Applied Physics, Volume 86, Issue 4, 1999, pp. 1860-1866 (Non-Patent Reference 2); A. Polian et al., “Elastic Constants of Gallium Nitride,” Journal of Applied Physics, Volume 79, Issue 6, 1996, pp. 3343-3344 (Non-Patent Reference 3); A. F. Wright “Elastic Properties of Zinc-Blende and Wurtzite AlN, GaN, and InN,” Journal of Applied Physics, Volume 82, Issue 6, 1997, pp. 2833-2839 (Non-Patent Reference 4); K. Shimada et al., “First-Principles Study on Electronic and Elastic Properties of BN, AlN, and GaN,” Journal of Applied Physics, Volume 84, Issue 9, 1998, pp. 4951-4958 (Non-Patent Reference 5).    Non-Patent Reference 1: R. B. Schwarz et al., “Elastic Moduli of Gallium Nitride,” Applied Physics Letters, Volume 70, Issue 9, 1997, pp. 1122-1124.    Non-Patent Reference 2: T. Deguchi et al., “Structural and Vibrational Properties of GaN,” Journal of Applied Physics, Volume 86, Issue 4, 1999, pp. 1860-1866.    Non-Patent Reference 3: A. Polian et al., “Elastic Constants of Gallium Nitride,” Journal of Applied Physics, Volume 79, Issue 6, 1996, pp. 3343-3344.    Non-Patent Reference 4: A. F. Wright, “Elastic Properties of Zinc-Blende and Wurtzite AlN, GaN, and InN,” Journal of Applied Physics, Volume 82, Issue 6, 1997, pp. 2833-2839.    Non-Patent Reference 5: K. Shimada et al., “First-Principles Study on Electronic and Elastic Properties of BN, AlN, and GaN,” Journal of Applied Physics, Volume 84, Issue 9, 1998, pp. 4951-4958.